This invention relates to the repair of mitral and tricuspid valves exhibiting valve regurgitation and more particularly to a device and method suitable for a less invasive repair of a mitral or tricuspid heart valve.
Human beings have a closed circulatory system in which oxygen-rich blood is almost completely segregated from oxygen-poor blood. The primary purpose of the circulatory system, which is also referred to as the cardiovascular system and consists of the heart, blood vessels, and blood, is to provide oxygenated blood to the organs throughout the body and to the lungs. The heart contains two ventricles, which are chambers that pump blood out of the heart and into arteries that carry blood away from the heart and into the organs throughout the body. The heart also contains two atria, which are chambers that receive blood returning from the body. Veins carry the blood returning from the body into the right atrium. During a period called diastole, the blood from the right atrium drains into the right ventricle. The right ventricle then contracts during a period called systole and pumps blood through the pulmonic valve into the lungs. Oxygen-rich blood returns from the lungs via the pulmonary veins and fills the left atrium. During diastole, blood drains from the left atrium into the left ventricle. During systole, the left ventricle powerfully contracts and pumps the oxygen-rich blood into the aorta, which carries the oxygen-rich blood to arteries that carry the oxygen-rich blood to the organs throughout the body.
Between each atrium and ventricle is an atrioventricular valve that prevents the backflow of blood into the atrium during ventricular contraction. The atrioventricular valves on the left-hand and right-hand sides of the heart are known as, respectively, the mitral and tricuspid valves.
The mitral valve is located between the left atrium and the left ventricle and allows unidirectional blood flow from the atrium to the ventricle. The mitral valve has two leaflets that are attached to a semi-rigid ring or annulus. FIG. 1 is a pictorial diagram of the mitral valve annulus as viewed from within the left atrium. A coronary sinus 2 lies adjacent to a mitral valve annulus 4, to which is attached an anterior leaflet 6 and a posterior leaflet 8.
In a healthy heart, the anterior and posterior leaflets 6 and 8 close tightly during systole, the period of left ventricular contraction in which the left ventricle contracts to pump blood out of the heart into the body via the aorta. When functioning properly, the anterior and posterior leaflets 6 and 8 do not allow any of the blood being ejected from the left ventricle to flow backwards through the mitral valve into the left atrium. However, one consequence of a number of cardiac diseases is that mitral valve annulus 4 becomes dilated so that the anterior and posterior leaflets 6 and 8 cannot completely close during systole, thereby creating gaps 10 between the anterior and posterior leaflets 6 and 8. As a result, mitral valve regurgitation occurs, resulting in some of the blood being ejected from the left ventricle flowing backwards through the incompletely closed mitral valve leaflets and into the left atrium. The blood that flows backwards during mitral valve regurgitation increases the pressure in the left atrium and in the pulmonary veins and the lungs. The result of this increased pressure is congestion in the lungs, a major cause of congestive heart failure. Dilation of the mitral valve also results in distortion of the shape of the valve orifice. Decreasing the circumference of the dilated mitral valve annulus has been shown to decrease the severity of mitral valve regurgitation, which results in a decrease in morbidity caused by congestive heart failure.
Prior art attempts to decrease the severity of mitral valve regurgitation entail replacement or repair of the mitral valve. Valve replacement and repair have several drawbacks. Both procedures require open-heart surgery, which necessitates stopping the heart and diverting the bloodstream through a heart-lung machine (a process referred to as cardiopulmonary bypass). Open heart surgery is a very intrusive procedure with many potential complications and a long recovery time. Besides the risk of death or stroke, there is an increased risk of diminished cognitive function after cardiopulmonary bypass.
In the case of mitral valve replacement, the native mitral valve is surgically removed and is replaced by an artificial mitral valve sewn into the mitral valve annulus. Certain replacement valves have a high failure rate, and a consequent increased rate of morbidity. For example, the Bjork-Shiley 60-Degree and 70-Degree Convexo-Concave heart valves have received significant public attention because of their high failure rate. The flaw in the valves involves the metal struts that hold the curved disk that tilts back and forth inside the metal ring to regulate blood flow between the heart chambers. The struts have been shown to break, leading to valve failure.
In the case of mitral valve repair, a number of surgical techniques have been developed. The most common mitral valve repair entails sewing a mitral annuloplasty ring into the mitral valve annulus. The mitral annuloplasty ring has a smaller circumference than that of the portion of the dilated mitral valve annulus to which the ring is sutured. This suturing of the mitral valve annulus to the rigid or semi-rigid annuloplasty ring results in a xe2x80x9ccinching upxe2x80x9d or shortening of a portion of the circumference of the mitral valve annulus so that the mitral valve leaflets come together more completely during systole, thereby decreasing the severity of mitral valve regurgitation. There are various prostheses in use for mitral or tricuspid valve repair, and each of them has disadvantages.
Use of rigid annuloplasty ring prostheses is taught by Carpentier in U.S. Pat. No. 3,656,185 and Cooley in U.S. Pat. No. 4,164,046. Although widely used, these rigid angioplasty ring prostheses have received significant criticism regarding their inflexibility, which prevents the normal alteration in size and shape of the mitral annulus; their obstruction of the left ventricular outflow tract, which can decrease the dimensions of the left ventricular outflow tract; and the incidence of inflow obstruction, which is a complication usually associated with use of the rigid ring prosthesis in the tricuspid valve. In addition, rigid annuloplasty ring prostheses have the disadvantage of not being of adjustable size. Thus the surgeon has to accurately judge the correct size of ring needed to reduce the annulus circumference and produce a competent valve.
Adjustable annuloplasty rings have also been implemented, as taught by Reed in U.S. Pat. No. 4,489,446; Ahmadi, et al. in U.S. Pat. No. 4,602,911; and Angell in U.S. Pat. No. 4,042,979. Many of these adjustable rings have the disadvantage of being circular, which is not an appropriate shape, particularly for the mitral annulus.
Use of a flexible ring prosthesis is taught by Massana in U.S. Pat. No. 4,290,151; Carpentier, et al. in U.S. Pat. Nos. 4,055,861 and 4,917,698; Northup III in U.S. Pat. No. 5,593,424; Cosgrove, et al. in U.S. Pat. No. 5,350,420; Wright, et al. in U.S. Pat. No. 5,306,296; and Wright et al. in U.S. Pat. No. 5,201,880. One disadvantage of using the fully flexible annuloplasty ring is the fact that it can be shortened in the posterior segment only by the placement of plicating sutures. Judgment of the position, size, and spacing of these sutures requires skill and experience. Inappropriate suture placement in the anterior segment can cause undesirable intra-trigonal shortening. A second disadvantage of using the flexible ring prosthesis is that following the tightening of the drawstrings, a bulky knot is formed on the atrial surface of the ring. The knot lies directly in the blood flow path into the inflow side of the valve. Should a thrombus form on the knot, an embolus could result. Also, if the surplus drawstrings are cut too close to the knot, the knot may become undone. Conversely, should significant surplus drawstrings tails remain, abrasion of the valve leaflets could occur.
What is needed, therefore, is a safer and less traumatic method of decreasing the incidence of mitral or tricuspid valve regurgitation that does not necessitate open heart surgery, heart stoppage, cardiopulmonary bypass, or replacement valve insertion.
An object of the present invention is, therefore, to provide a less invasive, safer method of decreasing the severity of mitral or tricuspid valve regurgitation.
Different embodiments of the present invention, described by way of example, position a prosthetic device in a blood vessel, such as the coronary sinus surrounding the mitral valve annulus or the coronary vein surrounding the tricuspid valve annulus. The prosthetic device reduces the circumference of the mitral or tricuspid valve annulus causing the valve leaflets that attach to the annulus to close more completely, thereby decreasing the regurgitation of blood back through the incompletely closed valve leaflets during ventricular contraction. The prosthetic device may be inserted into a beating heart either percutaneously via the femoral, jugular, or subclavian vein or via the right atrium through a surgical incision in the vena cava without employing open heart surgery or cardiopulmonary bypass.
A first preferred embodiment of the prosthetic device is an elongated member that includes distal and proximal segments separated by an intermediate segment. Each of the distal and proximal segments has a recessed end into which a different end of the intermediate segment fits and a terminal end opposite the recessed end. A first rigid or semi-rigid length control wire or cable is anchored on the distal segment and has a threaded section that passes through a mated threaded aperture in the intermediate segment. Rotating the first length control wire causes the end of the intermediate segment to insert into or withdraw from the recessed end of the distal segment, thereby shortening or lengthening the prosthetic device. Optionally, a second length control wire that further aids in controlling the overall length of the prosthetic device may be attached to the intermediate segment nearer to the proximal segment. Attached to the distal and proximal segments are two anchor control wires, each of which is connected to a coil spring having a controllable pitch. The control anchor wires are concentrically wound around each of the terminal ends of the distal and proximal segments. Rotation of the anchor control wires widens or narrows the coil spring diameter to respectively anchor the prosthetic device to or disengage the prosthetic device from the coronary sinus.
A second preferred embodiment of the prosthetic device is an elongated member that includes distal and proximal segments that are connected by a pivot or hinge joint. The distal segment has a narrow intermediate section positioned between a free end section and an interior section in the form of a clevis fastener. The proximal segment has a narrowed end section and an interior tongue section that fits into the clevis fastener. A control wire anchored on the interior section of the distal segment has a threaded portion that passes through a mated threaded opening located on the tongue section of the proximal segment. Rotation of the control wire pivotally moves the distal and proximal segments closer to or farther from each other to, respectively, reduce or increase the circumference of the valve annulus. Reduction of the circumference of the valve annulus brings the two valve leaflets closer together and thereby decreases the severity of valve regurgitation.